"This is the first drug to reach this phase of study" in the treatment of hepatitis C, lead investigator Dr. Eric Lawitz of Alamo Medical Research and the University of Texas at San Antonio announced. VX950 is an oral, highly selective inhibitor of hepatitis C virus NS3-4A protease.

Previous two-week studies showed VX950 was highly effective and well-tolerated as monotherapy. The addition of peg-interferon-alfa-2a further boosted the strong antiviral effects after 14 days of treatment.

In this 28-day trial, ribavirin was added to VX950 plus peg-interferon in 12 treatment-naive patients with hepatitis C virus (HCV) genotype 1 infection. After the 28-day study period, patients continued on with standard therapy of peg-interferon and ribavirin.

The primary endpoint was viral suppression at 28 days. The secondary endpoint was the safety of combination therapy. "Two patients had undetectable viral levels after only two days of treatment with VX950," Dr. Lawitz announced, emphasizing the rapid anti-viral effect. At day 22, eight patients had undetectable levels and at 28 days, all 12 patients had undetectable levels of the virus.

"Protease inhibitors work at the other end of the replication process from the antivirals," said panel moderator Dr. John Vierling, of Baylor College of Medicine in Houston, Texas and president of the American Society for the Study of Liver Diseases. "Sustained viral suppression is tantamount to a cure," he told Reuters Health.

Enrollment of phase II studies on the duration of VX950 efficacy are due to begin in June, Dr. Lawitz said.